You Are Not Alone by Jermaine Jackson and My Friend Michael by Frank Cascio – review

Alien world … Michael Jackson at the 2006 World Music Awards in London. Photograph: Gareth Cattermole/Getty Images

Michael Jackson went to his grave pop's greatest enigma. He was arguably the most famous man in the world, but his own world seemed so utterly alien – the theme-park mansion, the plastic surgery, the rumours of paedophilia, the children conceived by artificial insemination, the erratic behaviour, not to mention the almost inhuman degree of talent – that it was impossible to work out what the man at the centre of it all was actually like. There's a chance that, after living 41 of his 51 years in the public eye, Jackson was as confused as anybody else. Yet two memoirs – one by his elder brother, the other by his former personal manager – claim to offer a definitive picture.

Neither does, although his brother's book is the more substantial and, initially at least, the more insightful of the two. Reading the section about Jackson's early life you wonder not why he became so weird, but how he didn't end up even weirder. His mother was a devout Jehovah's Witness – aged 12, Jackson was required to record an album of songs for Christmas, a holiday he'd never been permitted to celebrate – who swabbed her children with alcohol, smeared their faces with Vaseline in the belief it made them look "nice and shiny" and protected them from the winter cold by putting boiled potatoes in their coat pockets.

Meanwhile, the best that can be said of Joseph Jackson is that he isn't quite the grimmest figure in the pantheon of tyrannical fathers vicariously living their dreams of pop stardom through their children: that remains the Beach Boys' patriarch Murry Wilson, who beat his son Brian about the head so viciously he allegedly deafened him in one ear. Still, Jackson whipped his children with a belt and the cord from an electric kettle and forced them to spend hours pointlessly carrying cinder blocks from one side of the garden to the other. The Jackson 5 would rehearse for up to five hours a night after school – if one of them got a dance step wrong their father would order the offender to break a branch off a nearby tree and would then hit him with it. When he learned that the teenage Michael was self-conscious about the size of his nose, he began calling him Big Nose. Whatever else you think of how Jackson's face looked by the time his plastic surgeons had finished with it, you certainly couldn't have called him that.

It reads like a misery memoir, but Jermaine claims not to see it that way. He presents all this ghastly evidence then spends pages admonishing as "ridiculous" those who suggest that his father's abuse scarred his most famous son for life. Never mind that Michael was still telling interviewers that the thought of his father made him feel sick with fear. No: their father's discipline instilled in them a will to succeed; furthermore without it, the Jackson boys might have ended up involved with the gangs that ran riot in their corner of Indiana.

This kind of contradiction turns out to be the book's recurring motif. At one juncture, Jermaine angrily complains that Michael's famous relationship with Bubbles the chimpanzee was "no different" to that of "millions of dog and cat owners the world over", before going on to describe Jackson dousing the chimpanzee in Poison by Christian Dior and supplying him with his own wardrobe: Bubbles was apparently better dressed than Jermaine's children. But You Are Not Alone's detail on what you might call the Wacko years, those after Thriller's record-breaking success, is sketchy: after unexpectedly calling time on a trying final Jacksons tour, Michael seems to have gone out of his way to avoid his family. My Friend Michael (William Morrow, £16.99) handily takes up the slack. It's subtitled An Ordinary Friendship With an Extraordinary Man, but there seems to be nothing ordinary about the friendship at all. Frank Cascio was four when he first met Jackson: his father was the manager of the New York hotel where the singer stayed. The first time Jackson was accused of child molestation, Cascio's father's reaction was to pull his son out of school and send him to Tel Aviv to keep Jackson company on tour. He ended up an employee, trying to sort out business affairs so chaotic that they brought a man who had sold 750m records to the brink of financial ruin.

It's a largely uncritical account, and yet Jackson still cuts a strangely pathetic figure: a middle-aged man addicted to prescription drugs, obsessed with pranks and water balloon fights, hopelessly chasing the childhood that had been denied him. The most intriguing things about Cascio's book are the disparities with Jermaine's account. Both are adamant that he was not a child molester: so adamant in Jermaine's case that, during his brother's 2003 trial, he rang up CNN, demanded to be put on air and shouted "My brother is not eccentric!", which, with the best will in the world, feels a bit like ringing up CNN and shouting "I am not shouting!" But while Jermaine insists that Lisa Marie Presley was the love of Jackson's life, Cascio claims the singer told him their marriage was nothing more than a business arrangement.

Neither of them has much to say about the music, nor the remarkable burst of creativity that began with the Jacksons' 1978 album Destiny and culminated in the world-beating Thriller and Bad, nor the slow decline in quality that set in thereafter. They take it as read that his final album Invincible didn't sell as well as its predecessors because of a shadowy music industry conspiracy against him, never considering the more prosaic reason that it isn't very good. Jackson seems to have always had appalling taste in everything but music and choreography. The description of his singlehanded remodelling of the family home Hayvenhurst in You Are Not Alone is unwittingly hilarious ("a painted mural filled one wall … a cartoon version of Michael perched high in a tree reading a book with the title The Secret of Life"). Just as his increased wealth allowed him to pursue his passion for schlock to new heights at his Neverland ranch, so his success ensured it would gradually seep into his music as well: "Earth Song", with its deathless question "what about elephants – have we lost their trust?", Invincible's creepy "The Lost Children" and "Speechless". He was so rich and famous no one could tell him to lay off the children's choirs and tone down the Messiah complex a little. He was still at it just before his death: "I'm the light of the world", he sang on "This Is It", intended as the theme song for his 2009 London concert residency, but released posthumously.

You Are Not Alone's description of preparations for those concerts makes for a harrowing counterpoint to the glossy, posthumous documentary based around them. The book claims, not entirely convincingly, that indications of Jackson's ill-health in the year before his death – photographs of him being pushed in a wheelchair, his visible frailty at the press conference to announce the London shows – were "all part of a clever plan" to make his comeback seem more stunning. But midway through rehearsals his health declined dramatically, possibly as a result of being administered on a nightly basis the general anaesthetic that eventually killed him. In Jermaine's telling, a man barely capable of standing was pressured by promoters fearful of losing money into continuing work. Michael Jackson, it seems, ended his career as he began it: impossibly talented but terrified, bullied into singing and dancing whether he wanted to or not.